Microstructure and Wear Behavior of Nano-TiB_2p/2024Al Matrix Composites Fabricated by Laser Direct Energy Deposition with Powder Feeding

The purpose of this study is to investigate the effect of TiB2 content on the microstructure and wear behavior of nano-TiB2p/2024Al composites fabricated by laser direct energy deposition (L-DED). The dry sliding friction and wear behavior was evaluated using a ball-on-disk tribometer by sliding samples against a 6-mm diameter GCr15 (AISI52100) steel ball under applied loads of 2.2 N at room temperature. Microstructural characterization of the as-deposited 2024Al alloy showed the presence of oriented columnar grains. Once 3 wt% TiB2 particles were introduced, the as-deposited microstructure consisted of a mixture of columnar and equiaxed grains. It was found that the addition of TiB2 particles can significantly improve the wear resistance of L-DEDed 2024Al. For instance, the wear-rate of an 8 wt% TiB2p/2024Al matrix composite with full equiaxed grains is almost 20 times lower than that of the unreinforced alloy. A grain morphology-induced wear mechanism for the L-DEDed TiB2p/2024Al composites is proposed and is dominated by mutual oxidation and abrasive wear. The research results are beneficial to understand the wear mechanism of L-DEDed nano-TiB2p/2024Al matrix composites and can also provide theoretical guidance for the selection of TiB2 content.